U.S. patent number 4,676,274 [Application Number 06/706,728] was granted by the patent office on 1987-06-30 for capillary flow control.
Invention is credited to James F. Brown.
United States Patent |
4,676,274 |
Brown |
June 30, 1987 |
Capillary flow control
Abstract
Capillary flow of a principal fluid is controlled through the
medium of a control fluid. The two fluids are capable of forming
fluid/fluid interfaces therebetween in which the potential energy
states of the two fluids on either side of the interface are
different. Flow control of the principal fluid is effected by
changing the kind of fluid/fluid interface by reversing the
potential energy states of the two fluids at the interface or
interfaces therebetween.
Inventors: |
Brown; James F. (Clifton,
VA) |
Family
ID: |
26109133 |
Appl.
No.: |
06/706,728 |
Filed: |
February 28, 1985 |
Current U.S.
Class: |
137/806; 137/252;
422/501; 422/82; 422/947 |
Current CPC
Class: |
B01L
3/50273 (20130101); B01L 2200/0605 (20130101); B01L
2300/0816 (20130101); B01L 2300/1805 (20130101); B01L
2400/0406 (20130101); Y10T 137/2076 (20150401); B01L
2400/0688 (20130101); B01L 2400/0694 (20130101); G01N
35/1095 (20130101); Y10T 137/4651 (20150401); B01L
2400/0487 (20130101) |
Current International
Class: |
B01L
3/00 (20060101); G01N 1/00 (20060101); F15B
021/00 () |
Field of
Search: |
;137/806,251.1,252
;422/58,100,101,103 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Chambers; A. Michael
Attorney, Agent or Firm: Snyder; John P.
Claims
What is claimed is:
1. A fluid flow control system for controlling capillary flow of a
principal fluid through the intermediary of a control fluid, which
comprises;
capillary passage means for conveying the principal fluid by
capillary flow therein and for allowing introduction of the control
fluid thereinto;
means for defining at least two fluid/fluid interface locations
within the capillary passage means;
the principal fluid and the control fluid having different surface
energy levels;
the principal fluid at one of said locations in combination with
its contacting portion of said capillary passage means providing a
potential energy state which is different from the potential energy
state of the control fluid in combination with its contacting
portion of said capillary passage means at said one location so
that a fluid/fluid interface of one kind between the principal and
control fluids may be pressure stabilized at said one location;
the principal fluid at the other of said locations in combination
with its contacting portion of said capillary passage means
providing a potential energy state which is different from the
potential energy state of the control fluid in combination with its
contacting portion of the capillary passage means at said other
location so that a fluid/fluid interface of another kind between
the principal and control fluids which is opposite said one kind
may be pressure stabilized at said other location; and
control means for causing said control fluid selectively to form a
first pressure stablilized fluid/fluid interface of said one kind
between the principal and control fluids at said one location and
selectively to form a second pressure stabilized fluid/fluid
interface of said another kind between the principal and control
fluids at said other location so as to control capillary flow of
the principal fluid through said capillary passage means.
2. A fluid flow control system as defined in claim 1 wherein said
means defines a third fluid/fluid interface location.
3. A fluid flow control system as defined in claim 2 wherein said
control means forms pressure stabilized fluid/fluid interfaces
between the principal and control fluids at two of said locations
so as completely to block said capillary passage means and thereby
provide a valving action.
4. A fluid flow control system as defined in claim 3 wherein said
means defines a fourth fluid/fluid interface location.
5. A fluid flow control system as defined in claim 4 wherein said
control means provides closed valving actions at two of said
locations which are longitudinally spaced within said capillary
passage means and a venting action at another location between said
two locations.
6. A fluid flow control system as defined in claim 3 wherein said
control means provides closed valving actions at two of said
locations which are longitudinally spaced within said capillary
passage means and a venting action at another location between said
two locations.
7. A fluid flow control system as defined in claim 1 wherein said
fluid/fluid interface locations are closely adjacent each
other.
8. A fluid flow control system as defined in claim 7 wherein the
areas of said locations are dissimilar.
9. A fluid flow control system for controlling capillary flow of a
principal fluid through the intermediary of a control fluid, which
comprises:
capillary passage means having a first path for conveying the
principal fluid by capillary flow therein and a second path for
allowing introduction of the control fluid into said first
path;
means for defining at least one fluid/fluid interface location
within said first path and a second fluid/fluid interface location
at the junction of said second path with said first path;
the principal fluid and the control fluid having different surface
energy levels;
the principal fluid at said one of said locations in combination
with its contacting portion of said capillary passage means
providing a potential energy state which is different from the
potential energy state of the control fluid in combination with its
contacting portin of said capillary passage means at said one
location so that a fluid/fluid interface of one kind between the
principal and control fluids may be pressure stabilized at said one
location;
the principal fluid at said second location in combination with its
contacting portion of said capillary passage means providing a
potential energy state which is different from the potential energy
state of the control fluid in combination with its contacting
portion of the capillary passage means at said second location so
that a fluid/fluid interface of another kind between the principal
and control fluids which is opposite said one kind may be pressure
stabilized at said second location; and
pressure control means for exerting a first pressure on said
control fluid to form a first pressure stabilized fluid/fluid
interface of said one kind between the principal and control fluids
at said one location and for exerting a second pressure on the
control fluid to form a second pressure stabilized fluid/fluid
interface of said another kind between the principal and control
fluids at said second location so as to control capillary flow of
the principal fluid through said capillary passage means.
10. A fluid flow control system for controlling capillary flow of a
principal fluid through the intermediary of pressure control to a
control fluid, which comprises:
first capillary passage means for conveying the principal fluid by
capillary flow therein and for defining at least first and second
junctions within said capillary passage means at which pressure
stabilized fluid/fluid interfaces may be formed between the
principal and control fluids;
second capillary passage means intersecting said first capillary
passage means between said first and second junctions for conveying
the control fluid and for defining a third junction at which a
pressure stabilized fluid/fluid interface may be formed between the
principal and control fluids;
the principal fluid and said control fluid having different surface
energy levels;
the principal fluid at the first and second junctions in
combination with the portions of the first capillary passage means
with which it is then in contact having a potential energy state of
a sense different from the potential energy state of the control
fluid in combination with those portions of said first capillary
passage means with which it is then in contact so that the
fluid/fluid interfaces at said first and second junctions may be
pressure stabilized;
said principal fluid at the third junction in combination with that
portion of said second capillary passage means with which it is
then in contact having a potential energy state opposite to said
sense from the potential energy state of the control fluid in
combination with that portion of the second capillary passage means
with which it is then in contact so that the fluid/fluid interface
at said third junction may be pressure stabilized; and
pressure control means connected with said second capillary passage
means for selectively exerting a first control pressure on said
control fluid which forms a pressure stabilized fluid/fluid
interface between the principal and control fluids at said third
junction without causing the control fluid to fill said first
capillary passage means and block capillary flow of the principal
fluid therethrough and a second control pressure on the control
fluid which causes the control fluid to fill said first capillary
passage means between said first and said second junctions and form
stable fluid/fluid interfaces between the principal and control
fluids at said first and second junctions so as to block capillary
flow of the principal fluid through said first capillary passage
means.
11. A capillary flow metering system suitable for controlling the
flow of a principal fluid through the medium of a control fluid
comprising the combination of:
flow passage means for conveying the principal fluid and defining a
pair of spaced junctions;
each junction being formed between a first capillary surface and a
second capillary surface having different surface energy levels and
the principal fluid in combination with the first and second
capillary surfaces providing different potential energy states
which are respectively different from the potential energy states
of the combination of said control fluid with said first and second
capillary surfaces;
said junctions defining an upstream junction and a downstream
junction within said flow passage means;
inlet capillary passage means defining an inlet capillary surface
having a different surface energy level than said first surface for
resisting flow of said principal fluid into the inlet capillary
passage means while allowing the control fluid to be introduced
into the space between said junctions;
pressure control means for selectively controlling the pressure in
the control fluid in said inlet capillary passage means between one
pressure allowing flow of the principal fluid through the flow
passage means and a higher pressure introducing the control fluid
into said space to form fluid/fluid interfaces at the upstream and
downstream junctions which block the flow of said principal fluid
through said flow passage means; and
valve means adjacent said downstream junction for permitting a
predetermined volume of principal fluid to fill between said
junctions.
Description
BACKGROUND & BRIEF SUMMARY OF THE INVENTION
Prior Art
The closest prior art of which applicant is aware is as
follows:
U.S. Pat. No. 3,607,083; Thiers; Sept. 21, 1971
U.S. Pat. No. 4,233,029; Nov. 11, 1980
U.S. Pat. No. 4,254,083; Columbus; Mar. 3, 1981
U.S. Pat. No. 4,264,560; Natelson; Apr. 28, 1981
U.S. Pat. No. 4,271,119; Columbus; June 2, 1981
U.S. Pat. No. 4,310,399; Columbus; Jan. 12, 1982
U.S. Pat. No. 4,399,102; Karlberg; Aug. 16, 1983
U.S. Pat. No. 4,426,451; Columbus; Jan. 17, 1984
Although the above patents involve fluid flow systems which may
utilize capillary flow principles, the basic concept of shifting a
control fluid/principal fluid interface for the purpose of
influencing or controlling principal fluid flow is not present
therein.
Technical Field of Invention
The invention is concerned with principal fluid flow control within
a capillary system, in which the flow control is effected by change
in the kind of fluid/fluid interface between the principal fluid
and a control fluid. The principal fluid and the control fluids
have different surface energy levels so as to be capable of
providing a fluid/fluid interface therebetween. The change in the
kind of fluid/fluid interface, to effect flow control of the
principal fluid, is effected by reversing the potential energy
states of the principal and control fluids at the locations where
the fluid/fluid interfaces are formed, the potential energy states
being determined by the surface energy level of the principal fluid
or control fluid each in combination with the surface energy level
of the material with which it is contact at the location of the
interface in question.
More particularly, it relates to fluid flow control systems and is
concerned primarily with controlling capillary flow of one fluid
(hereinafter the principal fluid) through the intermediary of
pressure exerted on a second fluid (hereinafter the control fluid),
the principal and control fluids having different surface energy
levels and being capable of forming fluid/fluid interfaces
therebetween, and wherein the principal fluid normally flows
through capillary surface means with which it in combination
presents a different potential energy state than does the control
fluid in combination with that same surface. Likewise, the control
fluid normally is in contact with capillary surface means with
which it incombination presents a different potential energy state
than does the principal fluid in combination with such surface.
The flow control of this invention is effected by shifting or
moving one or more fluid/fluid interfaces from one location,
junction or border in which the interface or interfaces are
confined within capillary surface means associated with the control
fluid to another location or locations in which the fluid/fluid
interface or interfaces intrude into or are confined to be within
the capillary surface means associated with the principal
fluid.
The location or locations of an interface or interfaces, as the
case may be, is effected by pressure control of the control fluid,
specifically by variation of pressure operating upon the control
fluid in such sense as to compel a change of location of the
interfaces. At some lower pressure acting on the control fluid, the
interface or interfaces will be located at a position which permits
full flow of the principal fluid and at some higher pressure on the
control fluid, the interface or interfaces will be located to
intrude into or to block the capillary means containing the
principal fluid thereby respectively to impede or to block the flow
of principal fluid.
Prior to the intrusion of the control fluid into the capillary
means containing the principal fluid, a fluid/fluid interface will
be present at a location within the capillary means for the control
fluid which does not materially impede the flow of the principal
fluid. It is the intrusion of the control fluid into the capillary
means containing the principal fluid which causes a change in
location or locations of one or more fluid/fluid interfaces so that
it or they are shifted to be within the confines of the capillary
means containing the principal fluid thereby to impede or to block
the flow of the principal fluid.
It is a particular feature of this invention that the difference in
pressure which must be exerted on the control fluid to effect the
aforesaid shift in locations of the interfaces is relatively wide
and is not of critical nature. The control fluid may for example
have a very low pressure (e.g., atmospheric) acting on it when an
interface is in non-impeding location or locations. Although the
pressure acting on the control fluid when an interface is in
impeding or blocking location or locations must be increased to be
greater than the pressure acting on the principle fluid, its value
may vary over a wide range or "bandwidth" as used herein.
Therefore, it is not difficult to select a value of pressure which
will effect the requisite shift of interface location.
More particularly, where an impeding or blocking fluid/fluid
interface is formed, the principal fluid operating in conjunction
with the surface of the flow passage with which it is in contact at
one side of the interface represents a different potential energy
state than does the control fluid operating in conjunction with the
surface area of the flow passage with which it is in contact on the
other side of the interface. This factor is important to the
bandwidth characteristic referenced above.
According to another aspect of this invention, where the
fluid/fluid interfaces are formed, the aforesaid capillary surfaces
with which the two fluids are in contact are themselves of
different surface energy levels. For example, for a principal fluid
having a higher surface energy level than the control fluid and
operating in combination with a capillary surface means whose
surface energy level is also high, such combination of principal
fluid and high surface energy level capillary means presents a
lower potential energy state than does the combination of the
control fluid and such high surface energy level capillary surface
means, whereas the opposite is the case when the principal fluid
and the control fluid are in contact with the lower surface energy
level capillary surface means within which the control fluid
normally operates. Thus, it will be appreciated that such an
arrangement is conducive to the bandwidth feature noted above. That
is to say, for example, an interface which is concave into the low
surface energy capillary means will occur when the interface is in
non-impeding or non-blocking location and a concave interface into
the high surface energy capillary means will occur when the
interface is in impeding or blocking location.
More specifically, the invention is concerned with the capability
of controllably establishing one or more pressure stabilized
fluid/fluid interfaces between the principal fluid and the control
fluid at at least two or more locations within the flow passage
means in order to achieve a desired control function. To this end,
the invention contemplates the provision of at least two
fluid/fluid interface locations within the flow passage for the
principal fluid, which locations are defined between different
surface energy level portions of the flow passage, each such
location or junction defining a border between these different
surface energy level portions which allows a control fluid to be
introduced into the capillary flow passage means so as to form a
principal fluid/control fluid interface stabilized by and at such
border, the control fluid serving either to restrict the flow of
the principal fluid or to block flow of the principal fluid. In the
former instance, the arrangement operates as a flow rate restrictor
and in the second instance, as a control valve which, itself,
permits other and different devices to be constructed.
The invention contemplates that the interface may be stabilized at
the location or junction between a capillary passage and another
capillary passage of substantially the same diameter, the materials
defining the two surfaces being of different surface energy levels
and defining the border; that the interface may be stabilized at
the location or junction between a capillary passage and a passage
of substantially larger diameter, in which case the smaller
capillary passage itself defines the location, junction or border
which stabilizes the interface; and that the interface may be
stabilized at the junction between two surfaces of different energy
levels, which two surfaces are those defining two capillary
passages which may be of disparate diameters.
According to the present invention, plural locations, borders or
junctions as described above may be used at spaced positions within
the flow passage for the principal fluid initially to trap or
isolate a predetermined or known volume of the principal fluid and
thereafter to release this isolated volume of principal fluid for
further controlled flow thereof. This technique may be employed,
for example, to meter or to pump or displace known quantities of
the principal fluid.
In a particular embodiment of the invention, a device relates to
capillary flow control and in particular to controlling such flow
with respect to extermely small volumes of a principal fluid. By
extremely small volumes of principal fluid, as used herein, is
meant volumes which may be as small as in the order of one
picoliter.
Although not necessarily restricted thereto, the embodiments of the
present invention as are disclosed hereinafter are principally
concerned with a liquid/gas system in which either the liquid or
the gas may operate as the principal fluid while the other operates
as the control fluid.
According to the present invention, a representative liquid/gas
system comprises a capillary flow passage means whose capillary
surface is formed by a high surface energy level material such as
glass whereas the low surface energy surface area is formed by
material such as Teflon and wherein the high surface energy level
fluid is water and the low surface energy level fluid is air. In
this system, either the water or the air may be the principal
fluid.
Systems of the present invention may employ porous membranes which
function as the capillary flow passage means, in which case the
junction is located at one end of the capillary passage means which
are defined by the membrane.
The applications of the present invention are many and varied and
although a few examples of particular applications are specified
hereinafter, the invention is by no means limited thereto.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 is a diagrammatic view of a fluid flow system employing the
principles of this invention;
FIG. 2 is an enlarged section of the capillary flow control unit of
FIG. 1;
FIGS. 3, 3A, 4, 4A, 5 and 5A are enlarged views of single capillary
passages of FIG. 2 illustrating the locations and details of the
fluid/fluid interfaces during flow and non-flow conditions;
FIG. 6 is an enlarged section illustrating one form of a valve in
accord with this invention;
FIG. 7 is an enlarged view illustrating one form of capillary
junction illustrative of the invention;
FIG. 8 is an enlarged view illustrating another form of capillary
junction;
FIG. 9 is an enlarged view of a preferred type of configuration for
a valve;
FIG. 10 is identical to FIG. 9 but showing the valve in open
condition;
FIG. 11 is a view illustrating another form which the valve may
take;
FIG. 12 is an enlarged perspective view illustrating a valve
construction suitable for a microsystem;
FIG. 13 is an enlarged section illustrating a metering device in
accord with the invention;
FIG. 14 illustrates the device in FIG. 13 during transfer of the
metered fluid;
FIGS. 15 and 16 are directed to another embodiment of a metering
system;
FIG. 17 is a diagrammatic view illustrating the principles of a
microsystem according to this invention;
FIG. 18 is a diagrammatic view of another microsystem according to
this invention; and
FIG. 19 is a section illustrating a dynamic flow restrictor in
accord with this invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates an embodiment of the present invention utilizing
the flow control principles specified herein. This system is
intended for macro flow control, that is, it is intended to operate
to control relatively large flows as opposed to micro flow control
where, for example, the flow may be restricted to be within a very
small capillary system as might be embodied in a microscope slide
for individual cell manipulation.
As illustrated, the system shown includes the valve mechanism
indicated generally by the reference character 10 and shown in more
detail in FIG. 2 in association with a variable pressure pump 12
which pumps water under pressure in the discharge line 14, the
pick-up being through the inlet conduit extending to the water
reservoir indicated generally by the reference character 18. Thus,
in this case, water is the principal fluid and its flow is
controlled by the valve 10 by air acting as the control fluid so
that at the discharge flow passage conduit 20, there is a flow or
no flow condition dependent upon the condition of the valve 10
which will be described with greater particularity hereinbelow. The
system also includes a variable pressure air compressor 22
discharging through a manually controlled valve 24 to the air line
26 connected with the valve 10. The manually controlled valve 24 is
positionable so that either the pressure provided by the compressor
22 is present in the line 26 or the line 26 is vented to atmosphere
as indicated by the vent passage 28. The gauge G measures the
pressure in the line 26 when the air compressor 22 is connected
thereto through the valve 24.
The valve 10 shown in FIG. 2 is constructed in accord with the
principles of this invention. To this end, the three
polymethylmethacrylate plates 30, 31 and 32 are constructed and
arranged so that when layered together as shown in FIG. 2, the
three porous membranes 33, 34 and 35 are held in position as shown.
The membrane 33 is provided with a chamber 36 above it and a
chamber 37 below it. Similarly, the membrane 34 is provided with a
chamber 38 above it and a chamber 39 below it and, lastly, the
membrane 35 is likewise provided with a chamber 40 above it and a
chamber 41 below it. The three chambers 36, 38 and 40 are in
communication respectively with the lines 14, 20 and 26 and it will
be seen that the three chamber 37, 39 and 42 are in communication
with the common chamber 43 substantially as is shown.
As will be appreciated, the system shown in FIG. 2 is a water/air
system. FIGS. 3 and 3A are somewhat idealized illustrations
depicting a single one of the capillary passages through the porous
membrane 33. Likewise, FIGS. 4 and 4A are idealized and illustrate
a single one of the capillary passages through the porous membrane
34 and, lastly, FIGS. 5 and 5A show idealized representations of a
single one of the capillary passages through the porous membrane
35.
FIGS. 3, 4 and 5 illustrate the conditions at the capillaries of
the several membranes 33, 34 and 35 when the valve 10 is in the
shut-off condition. The porous membranes 33 and 34 are made of
Nylon and are wettable by the principal fluid, in this instance,
water. The membrane 35, however is made of Teflon and is
non-wettable by the principal fluid water. Thus, when the line 26
is pressurized, at the pressure P2, the air will initially flow
through the porous membrane 35 from the chamber 40 to the chamber
52 and thence to the chamber 43 to displace water therefrom which
is forced to pass through the two membranes 33 and 34 until the
conditions of FIGS. 3 and 4 are obtained. As shown in FIG. 3, the
water pressure P1 supplied by the pump 12 over the line 14 and
filling the chamber 36 is opposed at one end of the capillary
passage CT1 so that the air in the chamber 37 below the membrane 33
forms a meniscus at the lower end of the capillary passage CP1 as
is illustrated in FIG. 3 and which meniscus defines the water/air
interface IF1 as illustrated. It can be shown that if the pressure
P2 slightly exceeds the pressure P1, the interface IF1 is
stabilized and will be located at the lower end of the capillary
passage CP1 as is illustrated in FIG. 3 and correspondingly, the
flow of water through the line 14, through the membrane 33 and into
the chamber 43 and thence upwardly through the membrane 34 to the
line 20 will be terminated. At the same time, as is illustrated in
FIG. 4, the water pressure head P operating in opposition to the
air pressure P2 in the chamber 39 will form a further water/air
interface IF2 as is illustrated, thus preventing escape of air from
the chamber 43 and 39 through the porous membrane 34. In this
condition of the valve, the capillary passage CP3 through the
membrane 35 will pass the air under the pressure P2 substantially
as is shown, it being appreciated that the porous membrane 35 is
made of Teflon which is non-wettable by the principal fluid
water.
When the manual valve 24 is vented to atmosphere and the line 26
therefore is at atmospheric pressure, the conditions of FIGS. 3A,
4A and 5A prevail and flow of the principal fluid will pass from
the inlet line 14, through the valve 10 and out the discharge line
20. As shown in FIGS. 3A and 4A, water will flow first from the
chamber 36 and through the capillary passage CP1 into the chamber
37 and thence into the chamber 43 and into the chamber 39 where it
will pass through the capillary passage CP2 and thence into the
chamber 38 and out the outlet line 20. At the same time, backflow
of water from the chamber 42 to the chamber 40 and the vented air
line 26 is prevented by virtue of the Teflon membrane 35 as is
illustrated in FIG. 5A, the capillary passage CP3, as is
illustrated in FIG. 5A, allowing the atmospheric pressure in the
chamber 40 to oppose the water pressure P1 in the chamber 42 to
form a water meniscus within the capillary passage CP3 which
defines the interface IF3 substantially as is shown.
The Table below illustrates data gathered in operation of the
system of FIG. 1. The pump 12 is an FMI Lab Pump, serial no. 4p918,
rated at a maximum flow of 3 ML/MIN at 60 PSI and was obtained from
Fluid Metering, Inc., Oyster Bay, N.Y. The compressor 22 is of
standard design capable of providing air pressure at various
ratings from 0 to 80 PSI. In the Table below, the settings of the
water pump produce the flow rates as indicated.
TABLE 1 ______________________________________ Water Pump System
Control Gas Setting (0-9) Pressure (PSI) Observation of
______________________________________ 2 Vented to ATM Water Flow
of 0.8 ML/MIN 2 20-80 Flow Stopped 4 Vented to ATM Water Flow of
1.4 ML/MIN 4 30-80 Flow Stopped 6 Vented to ATM Water Flow of 2
ML/MIN 6 40-80 Flow Stopped 8 Vented to ATM Water Flow of 2.5
ML/MIN 8 55-80 Flow Stopped
______________________________________
The above table illustrates the bandwidth feature of this
invention. In each case of controlled flow, the pressure required
to terminate flow could be varied over a wide range without causing
the blocking flow interfaces to lose stability. The upper value of
80 psi in each case was dictated by the maximum pressure acquired
by the air compressor, but even at a flow rate near the maximum, a
pressure range of 25 psi was still available for control.
FIGS. 1-5A illustrate the basic principles of the present invention
wherein fluid flow control is obtained by controlling capillary
flow of the principal fluid through the intermediary of the control
fluid, the principal and control fluids having different surface
energy levels and being capable of forming a fluid/fluid interface
therebetween. In the embodiment shown in FIGS. 1-5A, not only does
the water have a higher surface energy level than does the air, but
the water operating in conjunction with the Nylon membrane 33 and
34 which are wettable by the water cooperate in combination
therewith to provide a lower potential energy state for that
combination than for the combination of the Nylon with air.
Similarly, for the Teflon membrane 35, its potential energy state
in combination with air is lower than that of the water in
combination with the Teflon. Thus, the stable menisci and
corresponding fluid/fluid interfaces IF1, IF2 and IF3 are defined,
substantially as is described and shown.
A modified form of the control valve shown in FIG. 2 is illustrated
in FIG. 6 which, as is the case with the FIG. 2 system is adapted
to handle relatively large flow rates of the principal fluids. In
this case, the three lines 14, 20 and 26 form a Tee with the
materials of the tubes 14 and 20 being formed of glass and being
provided with porous glass windows 50 and 51 which correspond
respectively with the membranes 33 and 34 by providing a plurality
of capillary passages CP1 and a plurality of capillary passages
CP2, as is shown. The conduit 26 is formed of Teflon material 52
and is provided with a Teflon window indicated generally by the
reference character 53 which corresponds to the Teflon membrane 35
to provide the plurality of capillary passages CP3. As is the case
with FIG. 2, the FIG. 6 construction shows a fluid control system
in which water is the principal fluid and air is the control fluid
and shut-off is obtained as depicted in FIG. 6.
FIGS. 1-6 illustrate one kind of junction which is capable of
defining a border at which a fluid/fluid interface is stabilized.
This is further illustrated in FIG. 7 wherein the capillary tube 60
is joined with the capillary tube 61. Both of these capillary tubes
are shown as formed of high energy material such as glass and the
fluid 1 or principal fluid is water whereas the fluid 2 or control
fluid may be air or another gas, i.e., it is a fluid whose surface
energy level is different from (lower than) the surface energy
level of water. The junction at which the interface IF4 is
stabilized is defined at the mouth of the capillary passage means
defined by the capillary 60 because of the abrupt opening thereof
into the much larger passage defined by the capillary 61. The
capillary passage defined by the tube 60 is of 10 microns and the
inside diameter of the tube 61 is of 20 microns in the particular
situation shown. The capillary surfaces are more wettable by the
water than by the gas and for this reason little or no principal
fluid pressure is required to displace the control fluid from the
larger capillary 61. However, control fluid 2 pressure is required
to displace the principal fluid 1 from either capillary, this fluid
2 pressure being inversely related to the capillary radius. For the
two fluid system such as water and air in the capillaries as
described above made of glass, the transition pressure at the
junction of the two capillaries is about 6.0 PSI. That is to say,
the control fluid pressure must exceed the principal fluid pressure
by about 6.0 PSI in order to form the stabilized fluid/fluid
interface IF4 illustrated. If the materials of the two capillaries
60 and 61 are such as to be non-wettable by the principal fluid,
i.e., made of low surface energy material such as Teflon, similar
transition pressures as expressed above obtain but with opposite
polarity because the fluids 1 and 2 exchange surface energy
properties. Stated otherwise, the interface IF4 would be convcave
into the confines of the capillary 61 but would still be stabilized
at the junction defined at the mouth of the capillary 60. The
reason for the reversal of direction of the interface is that the
potential energy state for the combination of the high surface
energy level fluid (water) and the now low surface energy level
capillary surface (Teflon) provides a higher potential energy state
than does the low surface energy level fluid (air) in combination
with the low surface energy level Teflon, rather than the reverse
for the case when the glass is present.
It will be appreciated that the junction illustrated in FIG. 7 is
akin to the plurality of junctions achieved in FIGS. 1-6 at each of
the capillary passages illustrated. That is to say, the junction is
such as to define a border at the downstream end of the principal
flow path defined by the capillary means with which it is
associated whereat the interface is formed and stabilized.
A further type of junction is shown in FIG. 8 wherein the glass
capillary tube 70 abuts and adjoins the Teflon capillary tube 71,
the capillary passages being of substantially the same internal
diameter as is shown. In this case, the junction is defined between
two materials of different surface energy levels to provide a
border at which the interface IF5 is formed and stabilized. In the
case of FIG. 8, the presence of the capillary 71 providing a
capillary surface of lower surface energy, even though it is of the
same diameter as the capillary 70, operates to produce the same
effect as the abrupt change in diameter in FIG. 7. The high surface
energy level fluid (water) operates in combination with the high
surface energy level capillary surface (glass) to provide a lower
potential energy state than the potential energy state of the low
surface energy level fluid (air) in combination with the high
surface energy level capillary surface afforded by the glass at the
capillary junction. Therefore, the interface IF5 is concave into
the capillary 70, as shown and the border defined at the junction
is, as is also the case in FIG. 7, sharply and well defined.
FIGS. 9 and 10 show a control valve construction which is
functionally equivalent to those shown in FIGS. 1-6, although, the
principal fluid flow rate in this case is extremely small because
all of the passages illustrated in FIGS. 9 and 10 are of capillary
size. As shown in FIG. 9, there are two capillary glass tubes
indicated by the reference characters 90 and 91 and joining them is
a Teflon capillary tube 92 having a Tee capillary stem 93 joined
thereto substantially as is shown. There are three possible
locations for stabilized interfaces in this configuration, two
which are indicated at IF6 and IF7 in FIG. 9 and the other of which
is at IF8 as in FIG. 10. The flow blocking condition is shown in
FIG. 9 wherein the control fluid pressure stabilizes the two
interfaces IF6 and IF7 at the locations defined at the borders
provided at the capillary junctions formed where the disparate
surface energy level materials 90, 92 and 91, 92 join. The flow
condition is illustrated in FIG. 10 where the control fluid
pressure is vented so that the interface IF8 is now located or
formed at the border defined at the junction between the Tee stem
93 and the main body portion 92. It should be noted that this
junction at which the interface IF8 is located in FIG. 10 is akin
to the type of junction illustrated in FIG. 7.
FIG. 11 is substantially identical to FIGS. 9 and 10 but, in this
case, the Teflon capillary 92' is of larger internal diameter to
provide a junction situation at which the interfaces IF9 and IF10
are located which is more in conformity with the description
according to FIG. 7. The border defined at the junction provided at
the mouth of the Tee stem 93 and whereat an interface is located in
the flow condition of the valve is identical to the situation for
the interface IF8 in FIG. 10. The advantage of this construction is
that the control gas pressure has a wider "bandwidth" as was
previously described, i.e., its pressure is not required to be so
precisely controlled in order to form and obtain the stabilized
interfaces IF9 and IF10 as would be the case if the capillary tube
90', 91' and 92' were of the same internal diameter as in FIGS. 9
and 10. It will be appreciated that the junction at which the
interfaces IF9 and IF10 are formed and stabilized are more akin to
those described in conjunction with FIGS. 1-6, i.e., at those ends
of the capillary tubes 90' and 91' where they contact the space
within the capillary tube 92' containing the control fluid.
Consequently, the bandwidth feature as is demonstrated in Table 1
above obtains. It should be noted that there are various ways in
which to achieve this bandwidth feature in microflow systems such
as is illustrated in FIGS. 9 and 10. For example, aside from the
use of an enlarged diameter capillary 92', an arrangement as in
FIGS. 9 and 10 may be used but with narrowing or restrictions at
the various junctions, see particularly FIGS. 13 and 14 for such an
arrangement. Obviously a combination of such arrangements may be
employed, see for example FIG. 12.
A practical version of a micro flow control valve according to the
present invention is illustrated in FIG. 12. In this Figure, the
capillary passages involved are formed by suitable etching or other
processes in a glass substrate 100 which is provided with the glass
cover plate 101. The substrate 100 with its cover plate 101 may
form a microscope slide on which an entire controlled flow system
for manipulating cells may be formed, as hereinafter more
particularly described.
Thus, the channel 102 formed in the substrate and completed as to
its capillary dimensions by the cover plate 101 is precision
machined by known techniques and is preferably provided with a
necked down portion 103 in its high surface energy level channel
102 before joining the low surface energy level channel 104. It
will be appreciated that the restriction provided by the necked
down portion 103 (and also at 105) is in conformity with the above
discussion regarding the bandwidth feature. The output channel
likewise has a necked down portion 105 and a wider channel 106
substantially as is shown. The control fluid channel 107 is
likewise necked down as indicated at 108 to merge with the channel
104.
As initially formed, both the substrate 100 and the glass cover
plate 101 provide high surface energy glass surfaces for the
capillary passages but as is indicated by the stipling in FIG. 12
on the substrate 100, same is treated to provide the low surface
energy surface and as is indicated by the dashed line on the cover
plate 101, a similar treatment of the underside of the cover plate
is provided in conformity with the plan view outline of the lower
surface energy surface for the control fluid. For example, this
treatment may take the form of the application of Teflon material
to the requisite surfaces as indicated.
Another embodiment of this invention utilizing the principles
described above is shown in FIGS. 13 and 14. In this embodiment,
two control valves in accord with this invention are combined to
trap a known volume of principal fluid therebetween. Then, the
control valves are again used to expel or pump this known volume of
the principal fluid down the capillary line when it is desired to
do so.
The material which provides the high surface energy capillary
surface is the material indicated generally by the reference
character 110 whereas the low surface energy material is indicated
generally by the reference characters 111, 112 and 113. The inlet
channel 114 defined by the material 110 is necked down as at 115 to
provide a stabilizing junction with bandwidth features as
previously described and it leads into the volumetric chamber 116
of the chamber section 117 and is thereafter necked down again for
bandwidth purposes as indicated by the reference character 118
where it joins the control valve assembly indicated generally by
the reference character 119. Donwstream of the control valve
assembly 119 is a further section of high surface energy material
110' which is necked down as at 120 opening into the discharge
channel section 121, again for bandwitdh purposes. Just downstream
of the necked down portion 115 the low surface energy material 112
forms a vent as shown and just upstream of the necked down portion
118 the low surface energy material 113 provides a further
vent.
FIG. 13 illustrates the filling stage of this embodiment of the
invention. While the principal fluid is filling the pump chamber
under the capillary flow of the principal fluid operating in
conjunction with the high surface energy material 110, both vents
125 and 126 are open whereas the control valve 119 is closed to
prevent the fluid from flowing beyond the assembly. The control
valve 119 is closed due to the exogenous gas pressure introduced
through the capillary passage 127 and interfaces are formed at the
downstream and upstream ends respectively of the necked down
portions 118 and 120. The interface at the downstream end of the
necked down portion 118 is indicated at 129'. When the volumetric
chamber 117 has been completely filled with the principal fluid and
the control valve 119 is still closed, it will be appreciated that
a known volume of the principal fluid is trapped within the chamber
117. At this time, the pump chamber is completely filled and the
interface 130 (shown in FIG. 14 but not in FIG. 13) will also be
present which prevents flow of the principal fluid through the
capillary 126. At the same time, the principal fluid cannot intrude
into the capillaries defining the vents 125 and 126 because of the
low surface energy level characteristics of the materials in 111
and 113 and the low surface energy level of the control fluid with
respect to the principal fluid.
In order to pump out the volumetric chamber 117, exogenous control
fluid pressure is introduced as is indicated in FIG. 14 through the
capillary passage 125 while the control valve 119 is opened by
venting its capillary passage 127 as indicated. Both of these
capillaries 125 and 127 are connected with suitable sources of
control fluid having pressure control means associated therewith.
It will be noted that in this embodiment, the capillary 126 is
always vented to permit proper operation during filling so that it,
in effect, is a passive element whose presence is nevertheless
essential. The control fluid introduced at 125 forms a stabilized
interface 128 at the downstream end of the necked down portion 115
and thereby prevents backflow of the control fluid therebeyond,
i.e., a valving action is effected. The interface 130 is already
present at the mouth of the capillary 126 where it joins the pump
chamber so that as the principal fluid is being expelled from the
pump chamber by the travelling interface 129, the only flow path
for the principal fluid is through the necked down portion 118.
When the travelling interface 129 reaches the downstream end of the
necked down portion 118, it is stabilized thereat as is indicated
at 129' in FIG. 13.
It will appreciated that the arrangement of FIGS. 13 and 14 allows
a predetermined quantity or volume of the principal fluid to be
trapped, held and thereafter released for further flow. Two valves
are involved, one of which is the main control valve 119 which
operates from closed condition in order to permit filling of the
pump chamber and to open condition to permit the metered outflow of
the trapped principal fluid, and the other of which is the combined
valving and expelling action effected by the capillary passage
125.
In order to illustrate the principles of FIGS. 13 and 14 on larger
scale, reference is had to FIGS. 15 and 16 which are functionally
equivalent thereto. Primed reference characters are utilized in
FIGS. 15 and 16 to designate generally corresponding portions with
respect to FIGS. 13 and 14. FIG. 15 shows the volumetric chamber
117' after complete filling thereof under capillary action, the
control fluid being vented both at 125' and 126' at this time so
that no exogenous control fluid pressure is functional to prevent
this capillary action. The control valve 119' is pressurized
through its capillary passage 127' to form the interface 140 and
the interface 141 which correspond respectively to the interface
129' in FIG. 13 formed at the downstream end of the necked down
portion 118 and the interface at the upstream end of the necked
down portion 120. When the capilary passage 127 of the control
valve 119' is vented as is shown in FIG. 16, and the capillary
passage 125' is subjected to exogenous control fluid pressure while
the capillary passage 126' remains vented, the valving interface
150 will form corresponding to the interface 128 in FIG. 14 formed
at the downstream end of the necked down portion 115 and,
ultimately, the interface 151 is formed which is functionally
equivalent to the interface 129' of FIG. 13. Whereas FIG. 13
employs necked down portions to attain the maximum benefits of the
bandwidth feature of this invention, FIGS. 15 and 16 do not. Thus,
whereas the interface 129' of FIG. 13 is located at the downstream
end of the necked down portion 118, the corresponding interface 151
of FIG. 16 is located at the upstream end of the portion 118'. The
stabilized interfaces 152, 153 and 154 of FIGS. 15 and 16 are
formed and stabilized by virtue of the fact that the material of
the relevant capillary passages 125', 126' and 127' are
hydrophobic, that is, not wettable by the primary fluid.
FIG. 17 is a diagrammatic view of a micro flow system which may be
made in accord with the principles generally described above in
conjunction with FIG. 12 and which may be used in, for example, a
cell manipulator system for use while being observed with the aid
of a microscope. The system of FIG. 17 employs both the control
valves 200 constructed in accord with the FIG. 12 shown and
designated respectively by the reference characters 200-205 in
conjunction with the capillary section 206 for main flow control
and the glass capillary section 207 which, in effect, is a
volumetric chamber corresponding to the chamber section 117 of FIG.
13. In the position of the assembly shown in FIG. 17, the valves
201 and 204 are in the active or shut-off state whereas the
remainder of the valves 200, 202, 203 and 205 are in the open or
inactive state. In this condition, both main flow and sample flow
is taking place. If, now, the small volume of sample reagent is
desired to be introduced into the main flow, the valves 200, 202,
203 and 205 are made active. This shuts off the sample into the
volumetric section 207 and also shuts off the sample output flow.
Also, the closing of the valve 200 shuts off the main flow and the
closing of the valve 203 shuts off the main flow. If, now, the
valve 204 is deactivated, the gas supplied to the valve 202 will
pump the entrapped sample in the section 207 through the valve 204
and into the main flow outlet indicated. Similarly, if the valve
203 is deactivated whereas the valve 200 is activated, the
predetermined volume of the section 206 of the main flow will be
injected into the main flow outlet.
As will readily be appreciated from a study of FIG. 17, it is
relatively simple utilizing the principles of this invention to
manipulate media and reagents in any desired fashion and with
respect to this, reference is directed to FIG. 18 wherein a cell
manipulator of extremely small size is illustrated. As shown, four
pumps indicated generally by the reference characters 300, 301,
302, and 303, all constructed in accord with the principles shown
in FIG. 13 are employed. In addition, control valves 309-317
constructed in accord with the principles described in conjunctin
with FIG. 12 are also employed. As indicated, the entire assembly
is formed on a single substrate indicated by the reference
character 320 and a suitable cover plate generally in accord with
the principles disclosed in conjunction with FIG. 12.
FIG. 18 has been simplified somewhat for the purpose of clarity.
Thus, although the region 321 for cells and media supply is
illustrated as being contained within the unit 320, it is to be
understood that this supply will in reality be externally supplied.
The same is true for the regions 322, 323, 324, and 325. All of
these would normally be located separate from the substrate 320
containing the micro flow and manipulator system. In fact, the
region 325 shown as a single region would usually be comprised of
several regions respectively communicating with the individual
pumps 300, 301, 302 and 303.
In addition to the above, the system includes the filters 326, 327
and 328 to aid in the cell selection and manipulation processes.
The filter 326 may comprise individual "islands" spaced apart about
30 microns, for initial cell selection. Thus, as that area of the
system surrounding the filter 326 is being viewed through a
microscope with cells in media passing the filter 326 from region
321 toward region 322, a cell may be tentatively selected by
opening the valve 314 to allow such cell and media to flow
therethrough and into the cell select region 329. Now the smaller
bracketed area may be viewed under increased magnification. The
islands of the filters 327 and 328 are spaced apart about 5 microns
so that a cell cannot pass therethrough. If the cell is not desired
for further study, it may be rejected by opening the valves 311 and
312 and operating one of the pumps 301-333 and flushing it to
waste. If the cell is desired for further manipulation, the valves
310 and 311 are opened and one of the pumps 301-313 operated to
flush it toward the region 324 whereas the pump 300 ultimately
flushes it into the region 324. The reason for the plurality of
pumps shown is that once a cell has been selected, a selection of
one or more reagents or media to be contacted with it may be
desired. Thus, the several pumps should individually be connected
to these several supplies rather than to the simplified single
supply region 325 as shown.
A further embodiment of the invention is illustrated in FIG. 19
which shows an automatic flow regulator system. The system as
illustrated is a water/air system and the material indicated at 400
is of glass whereas that of 401 is of Teflon, although it is to be
understood that other and different arrangements in accord with the
principles disclosed herein may be employed. The two capillary
passages 402 and 403 are joined through the restricted or necked
down capillary passage 404 in order to form a venturi effect due to
the continuous flow of the water from left to right in FIG. 19. The
L-shaped leg 405 formed of Teflon preferably is necked down at 406
where the capillary passage 407 intersects the necked down section
404. The free end of this section 405 is vented, preferably through
the necked down portion 408. The glass section 409 defines a
capillary passage 410 which intersects the capillary passage 407.
Under non-flow conditions, the Teflon side tube 401 of the venturi
is filled with air and the glass side tube 409 is filled with
water. As water flows through the venturi 404, water rises in the
section 409 to intrude within the capillary passage 407 which traps
air between it and the necked down portion 406 and causes the air
to form a meniscus or interface 420 as shown. This interface
restricts the venturi section 404 and regulates the flow through
the system, automatically or in a dynamically regulated fashion as
dictated by the flow rate of the principal fluid. It will be
appreciated that proper configuration of the Teflon tube section
401, i.e., by tapering it, undulating it, etc. will alter the
flow/restriction relationship.
* * * * *